This invention relates to machines for cleaning carpet by applying a cleaning solution (commonly called a shampoo), brushing or scrubbing the cleaning liquid into the carpet, and using suction to recover a portion of the shampoo and entrained dirt.
The best known prior art in this area is probably the so-called "steam cleaner", which has a carriage unit connected to a multi-element wand incorporating both a pressurized hose used to spray shampoo onto the carpet and a metallic vacuum inlet head that an operator scrubs across the carpet to suck up liquid and entrained dirt. The carriage contains a shampoo feed tank, a pump receiving cleaning liquid from the feed tank and supplying it under pressure to the spray nozzle, and a "wet-vacuum unit" comprising a blower and a recovery tank. The shampoo, in the case of a steam cleaner, is a dilute heated detergent solution comprising an emulsifier and a de-foaming agent.
A more closely related prior art carpet cleaning machine is one of the rotary brush type, disclosed by Hughes et al. in U.S. Pat. No. 3,686,707 and by Hughes in U.S. Pat. No. 3,797,065. These rotary brush machines provide better cleaning with less damage to the carpet and less operator fatigue than can steam cleaners. Rotary brush cleaners are also referred to as "foam cleaners" because they conventionally use a fairly concentrated detergent solution, comprising a foaming agent, as the shampoo.
In U.S. Pat. No. 3,686,707 Hughes et al. teach the addition, to a scrubbing machine of the type having a downwardly facing brush journaled for rotation about the shaft of a brush motor, of a tubular extractor ring mounted about the periphery of a brush-housing body by a compliant attachment means permitting the ring to oscillate about a horizontal transverse axis. The rotary scrubber taught by Hughes also comprises a cleaning liquid reservoir fixedly attached to a control handle, the reservoir feeding a cleaning solution onto the top surface of the brush. The disclosure of Hughes et al. is herein incorporated by reference.
In U.S. Pat. No. 3,797,065 Hughes teaches an improvement to the Hughes et al. machine that incorporates mounting a wet vacuum system above the brush motor. The wet vacuum system comprises a recovery tank, a blower driven by a blower motor, and a hose linking the recovery tank to the vacuum chamber extractor ring. The disclosure of Hughes is herein incorporated by reference.
There are several shortcomings of prior art rotary brush carpet cleaning machines that the inventor has sought to overcome. Cleaning solution flow in prior art rotary brush machines has been found to be inefficient because the shampoo is fed through a nozzle onto the top of a rotating brush near its periphery. Much of this shampoo is wasted by being thrown off the top of the spinning brush by centrifugal forces and only a small fraction of the shampoo follows the desired flow path through slits in the top of the brush that convey it to the brushed portion of the carpet.
Moreover, significant operator fatigue occurs in the operation of prior art rotary brush machines. One source of this arises from the placement of the shampoo feed tank on the machine's control handle. Although positioning the feed tank on the handle allows the operator to fill the tank without spilling shampoo into the blower motor, it requires that much of the weight of the filled tank be supported by the operator's arms.